Analysis for unloaded quality factor of a rectangular double-reentrant cavity with circular cylindrical ferrule for klystron using Wheeler’s incremental inductance rule

Closed-form formulation for the estimation of equivalent circuit capacitance and inductance of a rectangular double-reentrant klystron cavity with circular cylindrical ferrules was developed and used for arriving at the resonant frequency of the cavity. The closed-form expression for the cavity inductance and resonant frequency were subsequently used for estimating unloaded quality factor of the cavity using Wheeler’s incremental inductance rule. The proposed analysis was validated against 3D electromagnetic analysis and measurements for a typical rectangular klystron cavity operating in C-X-bands.